For the first time, a large-scale map of channel processes on rivers of the Crimean Peninsula is created, the territory of which in its natural conditions and anthropogenic impact significantly differs from other regions of Russia. The connection between channel and floodplain morphology and riverbed sediments with geological, geomorphological and hydrological natural conditions is reviewed, as well as with the strongest human impact dating back to the 4th century BC and associated both with water intake and with technogenic transformation of river channels. Six regions of the Crimea Peninsula, differing in the conditions of channel formation and channel regime, are marked. The data on the length of rivers, their slopes, river channel changes, flood regime and mudflow activity, on the hydraulic engineering measures (river canalization, bank protection, creation of water reservoirs, etc.) is provided. The analysis of research results, including the created map, determined the need to study the influence of massive human intervention on the conditions of river channels formation in order to prevent or neutralize its negative environmental consequences.

The article examines the features of the morphology of the middle and lower reaches of the Amur River channel. They are characterized by vertical channel deformations with different directions and intensities. The sediment accumulation is observed on most of the middle reach of the Amur (except for the section where the Maly Khingan ridge intersects, where the channel is incised, and floodplain don’t exist) and the entire lower reach of the Amur.  A weak incision of the river is observed only below the confluence with the Zeya River. Increased sediment removal from the artificial channel is fixed in the lower reach of the Amur near the sandy Belaya Mountain (in the 20th century) after the construction of a hydroelectric complex on it.  It led to a change from incision to accumulation in the first few tens of kilometers downstream, which has not yet manifested itself in the morphology of the river channel. Different directions of vertical deformations are recorded in the positions of the curves Q=f(H). This is reflected in changes in the type of the river channel and the relief of the valley bottom. With the directed accumulation of sediments, the Amur in its lower reaches is characterized by an excess of the low-water level above the floodplain surface, widespread floodplain multi-branching, the widespread formation of a complexly branched channel, and on the tributaries (except for the large rivers – Sungari and Ussuri) estuarine lakes-spills. The channel becomes incised according to the geomorphological type, but branched, downstream from the city of Komsomolsk-on-Amur, as the Amur river crosses the spurs of the Sikhote-Alin ridge. The alternation of wide-floodplain, adapted and incised sections of the riverbed also occurs against the background of the directed accumulation of sediments, which is manifested in channel branches, floodplain multi-branching and estuarine lakes on tributaries in the estuarine part of the Amur River. Thus, throughout almost the entire middle and lower reaches of the Amur River, systematic accumulation of sediments occurs. It is caused by negative tectonic movements and is interrupted in the middle reaches of the Amur River by incision when it intersects positive structures. Long-term (on a geological time scale) intensive accumulation of sediments determines the morphology and dynamics of the Amur riverbed even in those areas where its rates are reduced or it is replaced by weak incision.

We present the results of using the method of sedimentation traps (mats) in geomorphological monitoring of alluvial sedimentation rates in the floodplain of the Oka River. Only two spring floods between 2014 and 2021 inundated the central (high) floodplain, resulting in the accumulation of a 0.45 mm layer of sediments. We observed sedimentation on the low floodplain annually. The average thickness of the mineral (according to National Standard 25100-2020) sediment layer on the mats reaches 19.8 mm/year. Only silty-clay sediments are transported far from the Oka River channel, and accumulation of sandy particles was noted in the river channel zone. We determined that the high floodplain at the monitoring points is inundated typically within 15 days, which corresponds to an average flood according to the V.I. Shrag's gradation. In riverine areas, the direct interaction between stream water masses and bank soils can extend for 1–6 months and is highly dependent on the type of spring and flood parameters. This allows us to identify such sedimentation settings as areas with regular manifestation of fluvial morpholithogenesis, sensitive to fluctuations in the climate of the Oka basin.

This study investigates the distribution and influencing factors of six heavy metals (Cr, Zn, Ni, Cu, Pb, Cd) in water and sediments from the coastal areas of the Yangtze River estuary. Field surveys at seven sites revealed that heavy metal concentrations are significantly affected by physicochemical parameters such as temperature, pH, redox potential, salinity, and conductivity. Strong correlations among Cu, Cr, and Ni suggest common sources or pathways. The findings provide insights into heavy metal behavior in estuarine environments and offer technical support for pollution control and water quality management

Active work on the extraction of non-metallic building materials in existing quarries leads to deterioration of hydrological and navigation conditions. On the upper part of the Belaya River, the provision of guaranteed depths is reduced. Significant deformations of the river bed occurred due to the large number of quarries. A long period of time and almost complete abandonment of quarry workings in the riverbed is needed to restoring the natural course of riverbed processes and the water level in the river. 

In modern conditions, when maintaining ship passages on inland waterways, it is necessary

to take into account the natural course of the development of the channel process, seasonal and longterm deformations of channels, climatically conditioned changes in the characteristics of river flow, as well as anthropogenic changes in the water and channel regimes of ship rivers. The latter factor is manifested both as a result of engineering (technogenic) impact, as well a result of regulation of river runoff by hydroelectric facilities. Studies have shown that to date, in a number of sections of large navigable rivers of Russia, for these reasons, erosion cutting of channels and an irreversible decrease in low-water levels have occurred. In some sections of waterways, these changes became critical safe navigation, which required the reconstruction of existing ship-passing hydraulic structures and the construction of new low-pressure hydroelectric structures. Currently, the Gorodetsky locks are being reconstructed on the Volga River to ensure navigation on the limiting section from the target of the Nizhny Novgorod hydroelectric station to Nizhny Novgorod; Bagaevsky low-pressure hydroelectric complex is being built on the Don. The construction of the Krasnogorsk water-lifting hydroelectric complex on the Irtysh in the Omsk region has resumed. Possible options are being considered to solve the problem of ensuring navigation on the Kama River section from the Votkinskaya hydroelectric station to Kambarka. Studies of the speed regime of the river flow, carried out in the lower reaches of hydroelectric facilities, showed that with unsteady water movement in the lower reach, there is an activation of sediment transport, both in the summer observation period – in an open channel, and in winter, when water moves under ice.